Disc Brake Piston Coating to Prevent Plating Peel Under Braking Heat
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Solution Overview
Problem
The existing electroless nickel-phosphorous composite plating layer on vehicle disc brake pistons made of aluminum alloy is prone to peeling due to heat expansion differences between the piston and the base layer, affecting the piston's strength and operation feeling.
Innovation Solution
A piston with a covering layer comprising a first iron-phosphorous alloy plating layer and a second nickel-phosphorous alloy plating layer, including 10-30 volume percent resin particles, is formed using electrolytic and electroless plating respectively, with zincate treatment as pretreatment, to enhance adhesiveness and thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an electroless nickel-phosphorous composite plating layer is formed on the outer surface of an aluminum alloy piston, then good sliding characteristics with the piston seal are achieved, but the base layer peels off the piston due to heat expansion difference during braking
Solution Approach 1:
The covering layer is segmented into three distinct layers: an aluminum oxide layer formed by anodizing treatment, an intermediate layer formed by zincate treatment, and a surface layer of electroless nickel-phosphorous composite plating. This segmentation isolates the aluminum alloy substrate from direct thermal stress while providing gradual transition zones that accommodate differential thermal expansion, preventing peeling of the plating layer during braking operations.
Solution Approach 2:
The aluminum oxide layer and zincate intermediate layer serve as mediators between the aluminum alloy piston and the electroless nickel-phosphorous plating layer. These intermediate layers have thermal expansion properties that bridge the gap between the aluminum substrate and the nickel-phosphorous surface layer, absorbing thermal stress and preventing direct peeling while maintaining good sliding characteristics.
2Weight of moving object
If the piston is made of aluminum alloy to reduce vehicle body weight, then weight reduction is achieved, but the piston strength and adhesiveness of the covering layer deteriorate under braking heat
Solution Approach 1:
The piston employs a composite structure combining aluminum alloy substrate with multiple protective coating layers (aluminum oxide, zincate, and electroless nickel-phosphorous). This composite material system maintains the lightweight advantage of aluminum alloy while the layered coatings provide enhanced surface hardness, wear resistance, and thermal stability, effectively compensating for the相对较低 strength of aluminum alloy under high-temperature braking conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides high strength and excellent operation feeling by ensuring good adhesiveness of the covering layer with the piston main body and maintaining non-adhesiveness with the piston seal, while withstanding braking heat.
Implementation Method 1
forming a first plating layer made of iron-phosphorous alloy on an outer surface of a piston main body made of aluminum alloy using electrolytic plating, the outer surface having undergone zincate treatment
Implementation Method 2
forming a first plating layer made of iron-phosphorous alloy on an outer surface of a piston main body made of aluminum alloy using electrolytic plating
Implementation Method 3
forming a second plating layer made of nickel-phosphorous alloy on a surface of the first plating layer using electroless plating
Implementation Method 4
a piston main body made of aluminum alloy and a covering layer formed on an outer surface of the piston main body, in which the covering layer includes a first plating layer made of iron-phosphorous alloy
Data Source
Figure 1~2
Figure 3A~3B
AI summary
A piston (7) has a piston main body (71) comprising an aluminum alloy, and a covering layer (20) formed on the outer surface of the piston main body (71), and the covering layer (20) has a first plating layer (21) comprising an iron-phosphorous alloy, and a second plating layer (22) comprising a nickel-phosphorous alloy formed on the first plating layer (21) .